let a = [1, 2, 3, 4, 5];
console.log(a.copyWithin(2)); // [1,2,1,2,3];
console.log(a.copyWithin(2, 3, 5)); // [1,2,2,3,3]
console.log(a.copyWithin(0, -2)); // [3,3,2,3,3]
